The present invention of development of biosensing granules will help in rapid characterisation of any effluent at on-site. Moreover, the invented biosensing granules are reusable for several times and involve less manpower. In addition, these biosensing granules are ecofriendly in nature, cost-effective and do not require any chemical or energy input and are hence easy to operate at field conditions.
The byproduct liquid streams from various industries contain different environmentally undesirable chemical compounds that adversely affect water bodies and groundwater reservoirs. The reduction of organic pollutants to environmentally acceptable limits is essential before discharging these effluents into the environment. This requires a prerequisite of measurement of organic content in these discharges, which help is estimation of pollutant strength, design of treatment methodology and disposable alternative, etc. The biodegradable organic strength in an effluent can be determined by calculating the ratio of biological oxygen demand (BOD) to chemical oxygen demand (COD). The prolonged time of analysis, undependable simulated experimental conditions and toxic nature of effluents limits its utilisation and subsequent decision making for selection of appropriate treatment methodology at on-site.
Effluent treatment options can be generally divided into the following categories—physical, chemical, biological and thermal. Among the above categories, biological treatment processes possess an edge over the others due to its potential to degrade the organic pollutants into simple and environmentally safe compounds such as methane, carbon dioxide and water that are eco-friendly in nature. Biotreatment of an effluent can be done by inoculation of appropriate microbial consortia and incubating either in anaerobic or aerobic conditions. Under aerobic conditions, microbial consorts present in the system utilise the oxygen and organic compounds of effluent for energy generation. The pollution concentration can be assessed by calculating the microbial activity in waste water. Thus, microbial activity in terms of respiration is an important indication to characterise the effluents under different biotreatability classes.
Several attempts have been made in part to determine the organic content of industrial effluents by chemical as well as by biological means so as to characterise the effluent, evaluate its biodegradability, and for choosing the appropriate treatment process option [Rogers, K. R. and Williams, L. R. (1995) Trends Anal. Chem. 14; 289-294]. The organic content of an effluent is generally expressed in terms of the amount of oxygen required to degrade the organic pollutants and is measured either by chemical or biological means. One of the thumb rules used in assessing the effluent's biotreatability criteria is the ratio of the biological oxygen demand (BOD) to that of the chemical oxygen demand (COD), which is normally a fraction. A low value of the BOD/COD ratio indicates the difficulty in biodegradation, while a high value represents the amicability of the wastes for biological degradation.
Biochemical oxygen demand is basically a bioassay procedure involving the estimation of oxygen consumed in a simulated system under standard prescribed conditions. BOD is performed in a BOD bottle of 300 ml capacity at 20° C. for 5 days by taking suitable aliquots of effluents in the presence of seed, either from raw sewage or treated effluent from waste water treatment plant and nutrients. The long time taken for analysis, undependable simulated experimental conditions, and the toxic nature of effluents offsets its application. In this context, COD comes into existence where organic matter in the effluent was oxidised by a strong oxidising agent at elevated temperature under acidic environment. This test requires approximately 3 hours for analysis and is not dependant on biological environment. However, this method has its own limitations, such as undependable accuracy, input of chemicals and energy and production of secondary effluent disposing problems, etc. This process of BOD/COD characterisation of an effluent is time consuming, a laboratory installation with special instrumentation to maintain the required temperature constantly, input of chemicals and energy and can not be generally utilised in the field conditions.
The other wastewater characterisation techniques for biodegradability are measurement of its inorganic nitrogen compound uptake rates. However, these methods will be applicable only for certain types of wastes. Moreover, they require special instrumentation to measure the respective inorganic compounds in the effluents. Recently, efforts are being made to combine an already advanced respirometric technique, the hybrid respirometer with titrimetric technique with limited success [Vanrolleghem, P. A. and Spanjers, H. (1998) Wat. Sci. Technol., 37; 237-246]. Several other researchers have also attempted to develop micro-organism based biosensors, which involve determination of microbial activity either by spectrophotometrically or electrochemically [Bains, W. (1994) Biosensors Bioelectronics., 9; 111-117; Corbisier, P., Thiry, E., and Diels, L. (1996) Environ. Toxicol. Water Qual., 11; 171-177; Silva, M. J., and Wong, J. L. (1995) Bioelectroch m. Bioener., 37; 141-148]. The drawbacks with all these techniques are long incubation periods and low initial response, etc. [Rogers, K. R. and Koglin, E. N. (1997) in Biosensors for Direct Monitoring of Environmental Pollution in Field, (ed. D. P. Nikolelis, U. J. Krull, J. Wang, and M. Mascini) Kluwer Publishers, Boston, 335-349]. Moreover, implementation of these technologies for on-site effluent characterisation is not possible [Koglin, E. N. and Williams, L. R. (1994) Trends. Anal. Chem. 13; 294-299]. Hence the development of a reliable methodology to rapidly estimate the oxygen required for biodegradation considerably promises advancement in environmental monitoring.